Substations in high and medium voltage power networks include primary devices such as electrical cables, lines, bus bars, disconnectors, circuit breakers, power transformers and instrument transformers, which are generally arranged in switchyards and/or bays. These primary devices are operated in an automated way via a Substation Automation (SA) system. The SA system comprises secondary devices, among which Intelligent Electronic Devices (IED) responsible for protection, control and monitoring of the primary devices. The secondary devices may be hierarchically assigned to a station level or a bay level of the SA system. IEDs on the bay level, also termed bay units, are connected to each other as well as to the IEDs on the station level via a communication network including an inter-bay or station bus for exchanging commands and status information.
A communication standard for communication between the secondary devices of a substation has been introduced by the International Electrotechnical Committee (IEC) as part of the standard IEC 61850 entitled “communication networks and systems for power utility automation”. For non-time critical report messages, section IEC 61850-8-1 specifies the Manufacturing Message Specification (MMS, ISO/IEC 9506) protocol based on a reduced Open Systems Interconnection (OSI) protocol stack with the Transmission Control Protocol (TCP) and Internet Protocol (IP) in the transport and network layer, respectively, and Ethernet as physical media. For time-critical event-based messages, such as trip commands, IEC 61850-8-1 specifies the Generic Object Oriented Substation Events (GOOSE) directly on the Ethernet link layer of the communication stack. SA systems based on IEC61850 are configured by means of a standardized configuration representation or formal system description called Substation Configuration Description (SCD).
Substation Automation (SA) systems include a number of basic SA functions for protection, control and monitoring of the substation. For functions protecting against a failure of a primary device, like breaker failure protection or bus bar protection, so called protection zones have to be considered. Protection zones are electrically connected parts of the switchyard, which are delimited by open disconnectors and open or closed circuit breakers. Accordingly, the relation between protection zones and switching devices, i.e. the disconnectors and circuit breakers, or their mutual assignment, is dynamically determined from the switchyard topology at single line level and from the present state of all disconnectors.
By way of example, if a bay circuit breaker which is tripped by a line protection function does not open because of an internal failure, a so-called breaker failure protection function is triggered in turn, and a trip signal is propagated to circuit breakers in protection zones adjacent to, i.e. to the left and right of, the failed circuit breaker. In other words, the task of breaker failure protection is to detect that a breaker has failed to clear a fault, and to trip all the remaining breakers feeding into the segment containing the fault in order to clear the fault for good. Likewise, the task of bus bar protection is to detect any fault on the bus bar, and to trip the breakers connected to the affected bus bar.
EP 1819022 A1 aims at minimizing the potential damage caused by the failure of a single central Intelligent Electronic Device (IED) responsible for calculating, assigning and storing information about switchyard zones of a high or medium voltage switchyard. To this end, a distributed switchyard zone management is introduced, comprising a distributed storage of the knowledge about the switchyard zones with assignments of individual switchyard elements or components to the various switchyard zones being stored on several IEDs.
EP 2262074 A1 is concerned with simplified engineering of protection lockout functionality in a Substation Automation (SA) system. Wiring complexity as well as supervision related engineering is replaced by including protection-zone related intelligence into a lockout function block at a breaker IED. The remaining configuration effort consists in assigning lockout function instances to respective protection zones, and in specifying for each protection function which protection-zone(s) it shall trip and reset after lockout. Hence for switchyard configurations and power networks where a protection function trips multiple breakers by using several bay control or protection devices a more efficient implementation of lockout functionality is possible.
For high availability of power in smart grids a fast load restoration, or load transfer, after a protection trip is important, to ensure that loads connected to a tripped, or isolated, bus bar segment are again provided with power without delay. Conventional load restoration systems are coupled to a previous load shedding action which remembers the shed loads, or rely on manual restoration of the loads in priority steps adapted to the available power reserve. Implementations of a fast load restoration after a bus bar trip also benefit from the IEC 61850 standard, which provides the necessary communication to the protection and control units in the switchyard without needing additional hardware wiring. Conventional implementations of load restoration require project, or substation, specific application logic and intensive testing.